Tree felling technique and shaped explosive charge employed therein



May 20, 1969 A. F. ABBOTT ET AL 3,444,811

TREE FELLING TECHNIQUE AND SHAPED EXPLOSIVE CHARGE EMPLOYED THEREINFiled Aug. 28, 1967 INVENTORS ALBERT E ABBOTT BRUCE J. HAS/{fly MARSHALLE. KLOP/CH m; @M& A T TOR'NE Y6 3,444,811 TREE FELLING TECHNIQUE ANDSHAPED EX- PLOSIVE CHARGE EMPLOYED THEREIN Albert F. Abbott and Bruce J.Haskin, Seattle, and Marshall E. Klopich, Renton, Wash., assignors toExplosives Corporation of America, Seattle, Wash., a corporation ofWashington Filed Aug. 28, 1967, Ser. No. 663,643 Int. Cl. F42d 1/00 US.Cl. 102-23 21 Claims ABSTRACT OF THE DISCLOSURE An improved method andshaped explosive charge for felling trees, which method comprisescutting a thin, flat pocket radially into the tree to be felled,preferably by making a thrust cut into the tree with a chain saw,inserting a shaped explosive charge into the pocket, and thereafterdetonating the charge. The shaped explosive charge comprises a generallyelongated, thin, flat container defined by a pair of parallel, planarside walls and a concavely-shaped, outwardly facing peripheral edge wallwhich functions to concentrate and direct the explosive shock wavecross-grain of the tree.

Background of the invention The present invention relates generally tothe art of tree felling, and more particularly to an improved method andshaped explosive charge for felling trees.

Numerous techniques have been devised for utilizing explosives to felltrees, but none has proven to be entirely effective. One such techniquecomprises strapping an explosive charge to the side of the tree to befelled in the vicinity of its base portion, or in a ring around theperiphery of the tree, and thereafter detonating the charge. Althoughthe shock wave from the explosion will propagate through the baseportion of the tree to effect severance thereof, the explosive blastalso disintegrates a substantial portion of the valuable base portion ofthe tree and often leaves an unsightly spike on the base of the felledtree which must be subsequently cut off. A further disadvantage of thistechnique is that an excessive amount of explosive material must beemployed since much of the explosive blast will be directed into spacerather than into the tree.

A somewhat improved known technique comprises wrapping several layers ofPrimacord, a cord-like explosive, around the tree and covering it with asteel shell overlay prior to detonating the explosive. Another techniquecomprises boring a cylindrical hole radially into the 'base portion ofthe tree, packing the hole with an explosive and thereafter detonatingthe explosive. While both of these techniques relatively reduce theextent to which the explosive shock wave is dissipated into thesurrounding space, they both cause disintegration of a substantialportion of the valuable base portion of the tree and leave an unsightlystump. Moreover, both of these techniques still require a substantialquantity of explosive to fell the tree. For example, approximately sixpounds of so-called C4 explosive are required to effect felling of atree 2 in diameter at the point of cut.

Summary of the invention In view of the foregoing, it is an object ofthe present invention to provide an improved method for explosivelyfelling trees which forms a relatively clean cut at the base portion ofthe tree, without disintegrating a significant amount thereof.

A further object of the present invention is to provide an improvedmethod for explosively felling trees which 3,444,811 Patented May 20,1969 requires only a minimum quantity of explosive material to beutilized.

Another object of this invention is to provide an improved,self-contained explosive charge unit especially adapted to be used inconjunction with the tree felling method of this invention.

The method of the present invention comprises cutting a generally planarpocket into a tree across the grain thereof, loading the pocket with anexplosive material, and thereafter detonating the explosive. By virtueof the configuration of the pocket cut in the tree, the shock wavegenerated upon detonation of the explosive material propagates throughthe tree along the plane of the pocket to make a relatively clean,smooth cut. Moreover, only a minimal quantity of explosive material isrequired.

The improved shaped explosive charge package of the invention isespecially adapted to fit into the pocket cut in the tree and comprisesa generally elongated, thin fiat container filled with either liquid orpowdered explosive. The peripheral edge wall of the container ispreferably V-shaped in cross section and outwardly facing to concentratethe shock wave generated upon detonation of the charge and principallydirect the shock wave through the tree along a single plane. The resultis a maximum cutting effect from a minimum quantity of explosive.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following more particulardescription of the preferred embodiment of the invention, as illustratedin the accompanying drawing.

Brief description of the drawing In the drawing:

FIG. 1 is a perspective view illustrating the manner in which a chainsaw is employed in the method of the present invention to cut a pocketin the tree to be felled;

FIG. 2 is a sectional plan view showing the shaped explosive charge ofthe present invention inserted in the pocket cut in the tree to befelled;

FIG. 3 is an enlarged plan view of one form of the shaped explosivecharge of the present invention;

FIG. 4 is a side elevation view of the shaped charge illustrated in FIG.3;

FIG. 5 is a further enlarged sectional view of the shaped chargeillustrated in FIGS. 3 and 4, taken generally along line 55 of FIG. 3;

FIG. 6 is a plan view of a modified form of the shaped explosive chargeof the present invention, wherein the central portion of the charge isreduced in width; and

FIG. 7 is a side elevation view of the shaped charge illustrated in FIG.6.

Description of the preferred embodiments To fell a tree 10 (FIGS. 1 and2) according to the method of the present invention, a generally flat orplanar pocket 12 is first cut in the tree. The pocket 12 has arelatively small thickness t compared to its depth d and width w, andextends radially into the tree 10 across the grain 14. Thus, thethickness t of the pocket extends generally in the direction of the treegrain 14, and the depth d and width w extend in directions across thedirection of the grain. The pocket should extend at least to thelongitudinal center line of the tree, and preferably about two-thirdsway through the tree, and preferably has a width less than half itsdepth. By way of example, to fell a tree which is about 30" in diameter,the depth, width and thickness of the pocket 12 may be approximately20", 4", and A to '/z of an inch, respectively. Thus, the depth of thepocket is suitably about five times its width, and the width is abouteight to sixteen times its thickness.

The pocket 12 may form a right angle with the longitudinal axis of thetree, as shown in FIG. 2, or it may form an acute angle with the axis tocontrol the direction in which the tree will fall when severance issubsequently effected.

While any suitable technique may be employed to cut the pocket 12 intothe tree 10, making a thrust cut into the tree with a chain saw 18(FIG. 1) has proven to be a particularly quick and efficient technique.This is accomplished by simply moving the chain 20 and its carrier 22radially into the tree 10, point first, so that the chain cuts acrossthe tree grain 14. The cut pocket 12 consequently has dimensions (depth,width and thickness) corresponding to the dimensions of the portions ofthe saw chain 20 and chain carrier 22 which penetrate the tree. As notedabove, the angle that the pocket 12 forms with the longitudinal axis ofthe tree, and hence the angle that the chain saw carrier 22 forms withthe trees axis when cutting the pockets, aids in determining thedirection in which the tree will fall when severance is subsequentlyeffected.

After the pocket is formed, explosive material is inserted into thepocket 12 of the tree 10 and is thereafter detonated. Due to theconfiguration of the pocket 12, the shock wave from the explosive blasttravels through the tree principally in a direction parallel to thedepth-width plane of the pocket to sever the tree. Very little of thetree is disintegrated in the process.

While various types of explosive materials, including explosive liquidsand particulate materials, may be packed into the pocket 12 anddetonated to effect felling of the tree 10, the novel shaped charge 30shown in FIGS. 3-5 is particularly effective when used in conjunctionwith the method described herein. The charge comprises a flexiblecontainer 32 (suitably fabricated from a metal such as aluminum sheet orfrom a molded plastic such as polyethylene) defined by a pair ofgenerally planar, parallel side walls 34, 36 and a peripheral edge wall38 filled with explosive material 40.

The peripheral edge wall 38 is concavely-shaped, preferably V-shaped,and outwardly facing. When the charge is detonated, this configurationof the peripheral edge wall 38 directs and concentrates the shock wavegenerated along a plane which extends through the V or center of thecharge, thereby giving maximum severing effect to the explosive shockwave and permitting a minimum quantity of explosive material to beemployed for any given size and specie of tree.

While the flexible container 32 may be packed or loaded with anysuitable liquid, slurry, particulate, or cast explosive composition, aliquid explosive composed of nitromethane, sensitized with 25%ethylenediamine has proven to be effective. The flexible containerpreferably should be thin-walled, particularly along its peripheral edgewall 38.

The tail end 44 of the shaped charge 30 is provided with a recess 46preferably sized to snugly receive a conventional blast detonator 48(FIG. 2). The forward end 50 of the charge is preferably curved to fitthe forward end of the pocket 12 cut by the chain saw 18 (FIGS. 1 and2). This curved shape of the forward end of the charge also functions tospread the explosive shock wave therefrom through a 180 azimuthal anglewhen the charge is detonated.

In use, a conventional blast detonator 48 is initially placed in therecess 46 in the tail end of the shaped charge 30, and the charge isinserted into the pocket 12 cut in the tree 10 to be severed. The chargeis then detonated in a conventional manner, and the shock wave generatedis concentrated and principally directed through the tree 10 by theconcave configuration of the peripheral edge wall 38 to effect severingof the tree. The cut surfaces of the tree are relatively nonshattered,and very little of the tree is disintegrated by the blast.

As can be seen from the foregoing, the shaped charge 30 constitutes aself-contained unit which may be fabricated beforehand rather than atthe tree site.

The modified shaped explosive charge 60 shown in FIGS. 6 and 7 isdesigned for use in felling trees having a soft center core, and differsfrom the charge 30 of FIGS. 3-5 in only one respect. The Width dimensionof the charge is reduced in its central portion 62. This configurationreduces the amount of explosive material used in the charge, therebyreducing its cost. The shaped charge 60 is identical to the shapedcharge 30 of FIGS. 3-5 in all other respects. When the charge 60 isinserted into the pocket cut in a soft core tree and detonated, theshock wave from the forward and rear portions of the charge will besufiicient to effect severance of the tree.

While the foregoing description is principally directed to the fellingof live trees by an explosive shearing action near ground level, it willbe understood that the disclosed method and the flat, elongate explosivecharge also have like utility for tree topping and/or severing othertreelike bodies, such as logs, pilings, poles or large cut timbers,simply by way of further example.

What is claimed is:

1. A method of severing a tree or the like having a longitudinal centerline, comprising the steps of cutting a cross-grain, generally planarpocket into the tree at a substantial angle relative to the center linethereof, said pocket having a relatively small thickness extendinggenerally along the direction of the grain of the tree, and having adepth and width extending generally in directions across the grain ofthe tree, the depth of the pocket being at least about equal to theradius of the tree in the area of the pocket, the width of the pocketbeing less than half of the depth of the pocket and at least about eighttimes the thickness of the pocket;

loading the pocket with an explosive material; and

detonating the explosive material.

2. The method of severing a tree or the like according to claim 1,wherein the step of cutting the pocket in the tree comprises cutting thepocket to a depth equal to at least about two-thirds of the diameter ofthe tree in the area of the pocket.

3. The method of severing a tree or the like according to claim 1,wherein the step of cutting the pocket in the tree comprises cutting thepocket to extend into the tree along a plane generally perpendicular tothe longitudinal center line of the tree.

4. The method of severing a tree or the like according to claim 1,wherein the step of cutting the pocket in the tree comprises cutting thepocket to extend into the tree along a plane which forms an acute anglewith the longitudinal center line of the tree.

5. The method of severing a tree or the like according to claim 1,wherein the step of cutting the pocket in the tree comprises making athrust cut into the tree with a chain saw.

6. The method of severing a tree or the like according to claim 1,wherein the step of loading the pocket with explosive material comprisessubstantially filling the pocket with a liquid explosive.

7. The method of severing a tree or the like according to claim 1,wherein the pocket cut into the tree is defined by two substantiallyparallel side walls and a peripheral edge wall; and wherein the step ofloading the pocket with an explosive material comprises inserting ashaped explosive charge into the pocket; the shaped explosive chargehaving generally flat side Walls contiguous to the side walls of thepocket and a concavely-shaped peripheral edge wall contiguous to theperipheral edge wall generally of the pocket.

8. An explosive charge package especially adapted to fit in across-grain, generally planar pocket in a tree or the like to effect thesevering thereof upon detonation of the explosive charge, said chargecomprising:

an elongate container defined by two substantially parallel,substantially planar side walls, a substantially semicircular end, and aperipheral edge wall, the depth of the container being at least abouttwice the width of the container and the width of the container is atleast about eight times the thickness of the container;

explosive material in said container; and

means in said container for receiving a blast detonator.

9. An explosive charge package according to claim 8, wherein at least aportion of the peripheral edge Wall of the container is thin-walled andcross-sectionally concave along its outer face.

10. An explosive charge package according to claim 9, wherein theperipheral edge wall of the container is V- shaped in cross sectionalconfiguration.

11. An explosive charge package according to claim 8, wherein saidcontainer is substantially filled with liquid explosive material.

12. An explosive charge package according to claim 8, wherein saidexplosive material at least principally comprises nitromethane.

13. An explosive charge package according to claim 8, wherein said meansfor receiving a blast detonator comprises a recess in the rear end ofthe container.

14. An explosive charge package according to claim 8, wherein saidcontainer is fabricated of molded plastic.

15. The method of severing a tree or the like, comprising: forming ahole in the tree near the base thereof the configuration of the holebeing with a thickness dimension extending generally along the directionof the grain of the tree, and with depth and width dimensions extendinggenerally in directions across the grain of the tree, the depth of thehole extending at least about half of the way through the tree and thewidth of the hole being less than half the depth of the hole and atleast about eight times the thickness of the hole; emplacing a cavitatedexplosive charge in the hole with cavitated portion(s) of the chargefacing generally cross-grain of the tree; and detonating the explosivecharge.

16. The method of claim 15, wherein said cavitated charge comprises anedge of relatively small dimension extending generally panallel to thegrain of the tree when the charge is emplaced, and said edge is ofgenerally concave shape.

17. In combination with a standing tree or the like; a sawn hole in thetree near the base thereof, said hole having a thickness dimensionextending generally along the direction of the grain of the tree andhaving depth and width dimensions extending generally in directionsacross the grain of the tree, the depth of the hole extending at leastabout half way through the tree and the width of the hole being lessthan half the depth of the hole and at least about eight times thethickness of the hole; and an explosive charge substantially fillingsaid hole.

18. The combination of claim 17, wherein said hole is a chain saw thrustcut.

19. The combination of claim 17, wherein said explosive charge iscontained in a thin-Walled container, configured to snugly fit in thehole.

20. The combination of claim 19, wherein said container has a peripheraledge wall of substantially V-shaped cross sectional configuration,facing generally cross-grain of the tree.

21. The combination of claim 19, wherein the explosive charge in saidcontainer is in liquid form.

References Cited UNITED STATES PATENTS VERLIN R. PENDEGRASS, PrimaryExaminer.

U.S. Cl. X.R.

